The research being carried out under this project is directed at metabolic studies of total parenteral nutrition (TPN) in infants. Specifically, the following areas are being studied (a) definition of optimal protein requirement in the content of TPN over a range of 2.0 to 3.0 g/kg/d, (b) identification of abnormalities of plasma amino acids produced by various intravenous amino acid preparations with the specific purpose of constructing dose-response curves using molar ratios of the plasma against corresponding intake ratios, (c) studies of the metabolic fate of 15N urea and 15N arginine in infants receiving TPN in order to compute the degree of recycling of urea as well as to compute net protein synthesis, (d) study of the essential fatty acid patterns in plasma of infants receiving conventional fat-free TPN infusates as well as the effects of intravenous fat emulsions upon such patterns. BIBLIOGRAPHIC REFERENCES: Heird, W.C., MacMillan, R.W., and Winters, R.W.: Total parenteral nutrition in the pediatric patient. In: Total Parenteral Nutrition. Edited by Fischer, J.E., Boston, Little Brown & Co., 1976, pp. 253-284. Heird, W.C., MacMillan, R.W., and Winters, R.W.: Total parenteral nutrition in infants. In: Symposium on Infant Nutrition. Edited by L.A. Barness, 1976.